1. Technical Field
The present disclosure relates to vehicle exterior environment recognition devices that recognize environment outside a vehicle. More specifically, the present disclosure relates to a vehicle exterior environment recognition device that is suitable for identifying a traffic indicator, such as a traffic light or a traffic sign.
2. Related Art
There are conventionally known a technique, such as collision avoidance control, which detects a specific objects including another vehicle and a traffic light located ahead of a vehicle and avoids a collision with the leading vehicle, and a technique, such as a cruise control, which recognizes the color of the traffic light and controls to maintain a distance between own vehicle and a leading vehicle at a safe distance (for instance, Japanese Patent No. 3,349,060).
Such a specific object is extracted from an image obtained by imaging an environment outside and ahead of the vehicle, based on the luminance and the distance data. For instance, Japanese Unexamined Patent Application Publication (JP-A) No. 2010-224925 discloses a technique to capture a color image outside the vehicle, group adjacent pixels, and recognize a light source, such as the traffic light, based on the distance, size, height, and a position of a grouped pixel with respect to a course of the vehicle.
The technique disclosed in JP-A No. 2010-224925 described above grasps the course of the vehicle from a lane line on a road surface based on a horizontal geometric model of the road surface in a real space, and determines a traffic light which exists on the course of the vehicle to be a traffic light for the vehicle. However, the lane line may be hard to be recognized according to weather, time, and/or environment outside the vehicle, or there is no lane line on the road surface from the beginning. In such a case, traffic indicators, such as traffic lights and traffic signs, which are used as control inputs to control the vehicle, may be difficult to be identified according to the environment outside the vehicle.
A possible solution is to predict a traveling path on which the vehicle travels, or a course taking a width necessary for the vehicle travel in consideration, based on a current traveling condition of the vehicle, such as a traveling speed, an angular speed, or a steering angle of the vehicle, without relying on the recognition results of lane lines and the like, and to identify the traffic indicators based on the traveling path or the like. However, the traveling path predicted based on the current traveling condition may not be in agreement with an actual traveling path. For instance, a steering operation for avoiding an obstacle or changing the lane is temporary and the actual traveling path is substantially a straight, but the traveling path may be predicted to be a curve based on the steering operation. If the traveling path predicted based on the current traveling condition is not in agreement with the actual traveling path, the traffic indicators to be used as the control inputs may not be able to be identified and may unintentionally be excluded from the control inputs.